A conventional image forming apparatus adopts an intermediate transfer method in which an image formation path is long. When a sheet feeding tray as a medium container is close to a transfer position of an image, it is necessary to start image formation before feeding a sheet from the sheet feeding tray. In order to maintain productivity of image formation even for such a positional relation, printing is performed by shortening an inter-sheet distance. However, there is a problem that, for example, when it is detected that there is no sheet in the sheet feeding tray, a formed image is wasted. In order to solve the problem, a number of remaining sheets of the sheet feeding tray is detected, and when the number of the remaining sheets reaches a predetermined amount, the inter-sheet distance is increased to be larger than that of normal setting and the timings for starting a sheet feeding operation and for starting an image formation operation are reversed (for example, see Patent Document: Japanese Patent Laid-Open Publication No. 2002-323839).
However, in the conventional technology, there is a problem that, when the number of sheets of the remaining medium has reached the predetermined amount, in order to increase the inter-sheet distance to be larger than that of normal setting, a transfer belt and a photosensitive body are caused to rotate more than that during normal printing and processing capability is reduced. A purpose of the present invention is to solve such a problem to suppress reduction in the processing capability even when the number of sheets of the remaining medium has reached a predetermined amount.